The invention relates to a deflecting arrangement having a first deflecting element for deflecting conveyable-article carriers, and having a second deflecting element for deflecting an endless drive belt for driving the conveyable-article carriers in a conveying arrangement, in particular overhead conveying arrangement, which comprises a running-rail guide for the conveyable-article carriers and is intended for transporting the conveyable-article carriers along a conveying route, the deflecting arrangement, in the installed state in the conveying arrangement, forming one of two spaced-apart deflecting stations around which the endless drive belt, which is driven for movement, runs as a loop, and the endless drive belt being guided along the route region from deflecting station to deflecting station for carrying along conveyable-article carriers along the conveying route.
A conveying arrangement having a deflecting arrangement of the generic type is known, for example, from EP 0 582 047 B1. This known conveying arrangement is an overhead conveying arrangement having at least one conveying loop comprising two end-side deflecting arrangements and running rails for straight-line travel along the respective conveying-route region from deflecting arrangement to deflecting arrangement. The conveyable-article carriers which are to be transported each have a carrier body which is essentially vertically aligned in the transporting position and has running rollers projecting from it on both sides and a bottom hook into which it is possible to fit the conveyable article which is to be transported. Upon movement of the respective conveyable-article carrier along a running rail, the conveyable-article carrier is supported in a laterally suspended manner on the running rail by way of one of its running rollers, the carrier being in drive connection, with a friction fit, with an endless friction belt by way of a protrusion beneath the running roller, said protrusion projecting from the carrier body in the direction of the running rail. The endless friction belt, which is designed as a flat steel belt, is guided on the running rail, by means of a guide, for movement along the conveying route and for carrying along relevant conveyable-article carriers with a friction fit. The deflecting arrangements according to EP 0 582 047 B1 are rotatable deflecting drums with vertically running axes of rotation. In the bottom region, each of the two deflecting drums, as an element for deflecting the friction belt, has a flat circumferential groove in which the endless friction belt is guided as it is deflected. Provided above the circumferential groove on each deflecting drum, as element for deflecting conveyable-article carriers, is a conveying flange which runs round the circumference. Said conveying flange serves for receiving conveyable-article carriers from a relevant running rail, during tangential advancement up to the deflecting drum, and for transporting the same upon deflection in accordance with rotation of the deflecting drum. For this purpose, the conveying flange engages in a lateral groove, which is bounded by two side webs and belongs to the relevant conveyable-article carrier, above the running roller supporting the conveyable-article carrier on the running rail, with the result that, finally, the top side web of the conveyable-article carrier rests on the top side of the conveying web and the conveyable-article carrier is thus supported on the conveying web in a laterally suspended manner for being carried along by the deflecting drum. It is possible to provide on the deflecting arrangement a transfer means which acts as a diverter and transfers the conveyable-article carriers from the deflecting drum onto a conveying route of another conveying loop. If such a transfer means is not present or has been rendered inactive, the conveyable-article carriers are deflected through 180xc2x0 by the deflecting drum and then transferred to a running rail again, in order for them to be moved in the direction of the relevant other deflecting arrangement.
For driving the endless friction belt, one of the two deflecting drums is usually driven in rotation by a drive motor. For the endless friction belt to be carried along by the driven deflecting drum as far as possible without slippage, it is necessary for the endless friction belt to be tensioned. In order to ensure reliable functioning of the conveying arrangement, it should be ensured that the operations of the relevant conveyable-article carriers being received from a running rail onto the conveying flange of the deflecting drum, and of the conveyable-article carrier being deflected and subsequently transferred to the next running rail, take place at defined locations of the conveying route. For this purpose, in the conveying arrangements of the type described in EP 0 582 047 B1, the deflecting drums, in accordance with the desired conveying route, were installed at constant distances from one another and the endless friction belts readjusted with suitable tension during installation.
On account of changes in the length of the endless friction belt, for example as a result of temperature fluctuations, wear, etc., however, the problem of increased slippage between the friction belt and deflecting drum may arise, in particular with relatively large built-up pressure in the case of a conveying arrangement in which conveyable-article carriers may optionally be accumulated on a running rail.
The object of the present invention is to provide a deflecting arrangement of the type mentioned in the introduction which, in a relevant conveying arrangement, in particular overhead conveying arrangement, allows readjustment of the tensioning of the endless drive belt in the event of changing operational conditions, for example temperature fluctuations, without the mutual geometrical relationships of the elements forming the conveying route changing.
In order to achieve this object, the invention proposes that, for the purpose of adjusting the tensioning of the endless drive belt, the second deflecting element be arranged on a mount such that it can be displaced relative to the first deflecting element between a first position, namely a position of reduced distance from the other deflecting station, and a second position, namely a position of increased distance from the other deflecting station.
Unlike the prior-art deflecting arrangement which is known from EP 0 582 047 B1 and has the conveying flange as deflecting element for the conveyable-article carriers and the circumferential groove as deflecting element for the endless drive belt on a common deflecting drum, it is the case with the deflecting arrangement according to the invention that the deflecting element for the conveyable-article carriers and the deflecting element for the endless drive belt are no longer coupled rigidly in respect of all degrees of freedom. The deflecting element for the endless drive belt can be displaced relative to the deflecting element for the conveyable-article carriers and to the other deflecting station, in order for the tensioning of the endless drive belt to be adjusted. In this case, there is no change in the mutual geometrical relationships of the elements forming the conveying route, with the result that the transfer points for the conveyable-article carriers between running-rail guide and first deflecting element remain at their defined locations.
According to one embodiment, provision may be made for the second deflecting element to be arranged on the mount such that it can be fixed in its respective displacement position. In this case, the belt tensioning can be adjusted manually in each case by the second deflecting element being displaced into a displacement position suitable for the desired belt tensioning and then being fixed in said displacement position.
According to a preferred configuration, the deflecting arrangement, however, has a prestressing arrangement which subjects the second deflecting element to a force which resiliently prestresses the second deflecting element in the direction of the second position, in order to tension the endless drive belt. The second deflecting element, rather than being fixed rigidly in its displacement guide, is thus adjusted in a respective displacement position by the counteracting forces of the prestressing arrangement and of the endless drive belt, with the result that the endless drive belt always undergoes well-defined tensioning. In the case of an extension in length of the endless drive belt, the prestressing arrangement forces the second deflecting element in the direction of the second position, the tensioning of the endless drive belt being maintained in the process. In the case of a temperature-induced shortening of the endless drive belt, the second deflecting element can then yield in the direction of its first position, with the result that excessive belt tensioning is prevented. It is possible to provide, within the context of the invention, means for the variable adjustment of the prestressing force of the prestressing arrangement.
The first deflecting element and the second deflecting element are preferably rotatably mounted deflecting wheels with mutually parallel axes of rotation, the two deflecting wheels preferably being arranged on a common mount.
The second deflecting element or deflecting wheel, which is provided for deflecting the endless drive belt, is expediently mounted rotatably on a carriage which is guided in a carriage guide provided on the mount, in order to mount the second deflecting element displaceably relative to the first deflecting element.
The prestressing arrangement preferably has a prestressing spring for producing the prestressing force, the prestressing spring acting between the mount and the carriage in order to prestress the second deflecting element in the direction of the second position. The prestressing arrangement may be constructed in a straightforward manner using such a prestressing spring. Alternatively, it would also be possible to use a prestressing arrangement in which the prestressing force is produced, for example, by pneumatic means.
The endless drive belt is preferably a friction belt for carrying along the conveyable-article carriers with a friction fit, as is known, for example, from EP 0 582 047 B1.
In an alternative embodiment of the deflecting arrangement for a conveying arrangement with chain drive, the endless drive belt is a drive chain in which the conveyable-article carriers can engage with a form fit.
The two deflecting wheels are preferably coupled to one another for joint rotation by a coupling arrangement, the coupling arrangement having a radial guide on one of the deflecting wheels and a coupling element, which engages in the radial guide in a displaceable manner relative to the same, on the other deflecting wheel. The deflecting wheel for the conveyable-article carriers is, in this way, carried along for joint rotation during rotation of the deflecting wheel for the endless drive belt, it being possible, on account of the displaceability of the coupling element in the radial guide, for compensation to take place in respect of the eccentricity of the axes of the two deflecting wheels. The coupling arrangement thus also functions when the second deflecting wheel is not located coaxially with the first deflecting wheel because said second deflecting wheel has been displaced relative to the first deflecting wheel by the prestressing arrangement.